Use of tetrafluoropropene based compositions

ABSTRACT

The invention relates to the use of a composition comprising a polyol ester-based lubricant and a refrigerant F comprising at least one tetrafluoropropene and at least one hydrofluorocarbon, in a heat transfer system containing a vapour compression circuit comprising an oil separator.

FIELD OF INVENTION

The present invention relates to the use of a composition based ontetrafluoropropene and at least one lubricant, in refrigeration, airconditioning and heat pump.

TECHNICAL BACKGROUND

The problems posed by substances that deplete the atmospheric ozonelayer were discussed in Montreal, where the protocol imposing areduction in the production and use of chlorofluorocarbons (CFCs) wassigned. This protocol has been amended to eliminate the use of CFCs andextend the regulation to include other products, includinghydrochlorofluorocarbons (HCFCs).

The refrigeration and air-conditioning industry has invested heavily inthe substitution of these refrigerants and hydrofluorocarbons (HFCs)have thus been marketed.

In the automotive industry, the air conditioning systems of vehiclesmarketed in many countries have moved from a chlorofluorocarbon (CFC-12)refrigerant to hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a)refrigerant, less harmful for the ozone layer. However, in view ofobjectives set by the Kyoto Protocol, HFC-134a (GWP=1430) is consideredto have a high warming potential. The contribution to the greenhouseeffect of a fluid is quantified by a criterion, GWP (Global WarmingPotential) which summarizes the warming power by taking a referencevalue of 1 for carbon dioxide.

Hydrofluoroolefins (HFOs) have a low warming potential and thereforemeet the objectives set by the Kyoto Protocol. JP 4-110388 discloseshydrofluoropropenes as a heat transfer agent.

In the industrial field, the most widely used refrigeration machines arebased on evaporative cooling of a liquid refrigerant. Aftervaporization, the fluid is compressed and then cooled in order to returnto liquid state and thus continue the cycle.

Lubricating oils are necessary to ensure the proper functioning of themoving mechanical parts, and especially to ensure the lubrication of thecompressor bearings. However, the refrigerant fluid, which is in contactwith the lubricant present on the moving parts, at each passage throughthe compressor, tends to carry a certain amount, which accompanies therefrigerant in its cycle, and is therefore found in the evaporator. Toovercome this problem of oil migration, it is common to use an oilseparation system, capable of purging the accumulated oil from the highpressure at the compressor outlet towards the low pressure (at thecompressor inlet).

Thanks to their thermal stability and their miscibility with HFOs,especially HFO-1234, POE oils are commonly used in heat transfersystems, especially in refrigeration and/or air conditioning.

However, due to good solubility of HFO-1234 in POE oils, a problem isfound on heat transfer systems having an oil separator: a relativelylarge amount of refrigerant remains trapped by the oil. Draining the oilinduces the return of trapped refrigerant from the compressor outletdirectly to the inlet of the latter. This results in a net loss ofefficiency for the system, since the entire refrigerant does not performthe refrigeration cycle in its entirety, and also results in adeterioration of the lubrication of compressors, especially of screwcompressors, due to lower amount of oil.

There is therefore a need to find new compositions making it possible,in particular, to overcome at least one of the aforementioned drawbacks.

DESCRIPTION OF THE INVENTION

The present invention relates to the use of a composition comprising apolyol ester-based lubricant, and a refrigerant F comprising at leastone tetrafluoropropene and at least one hydrofluorocarbon, in a heattransfer system containing a circuit vapour compression apparatuscomprising an oil separator.

Unless otherwise stated, throughout the application, the proportions ofcompounds indicated are given in weight percentages.

The compositions of the invention advantageously make it possible toimprove the efficiency of heat transfer systems comprising an oilseparator, particularly with respect to HFO-1234/POE oil compositionswhich are devoid of hydrofluorocarbons. The compositions according tothe invention also reduce the deterioration of the lubrication ofcompressors compared with HFO-1234yf alone, particularly due to therecovery of a higher quantity of lubricating oil in the separator.

In the context of the invention, the term “composition of the invention”is intended to mean a composition comprising a polyol ester-basedlubricant and a refrigerant F comprising at least one tetrafluoropropeneand at least one hydrofluorocarbon. The various compounds and ratios ofsaid compounds in the composition according to the invention aredescribed below.

Refrigerant Fluid

The refrigerant F according to the invention comprises at least onetetrafluoropropene (HFO-1234) and at least one hydrofluorocarbon.

Examples of the tetrafluoropropenes, include 1,3,3,3-tetrafluoropropene(HFO-1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf) and1,2,3,3-tetrafluoropropene (HFO-1234ye).

The tetrafluoropropene is preferably HFO-1234yf or HFO-1234ze.

The refrigerant F according to the invention can be prepared by anyknown method, for example by simply mixing the different ingredientstogether.

In the context of the invention, “HFO-1234ze” refers to1,3,3,3-tetrafluoropropene, regardless of whether it is cis (Z) or trans(E). The term “HFO-1234ze” therefore covers cis-HFO-1234ze,trans-HFO-1234ze, and all mixtures of the two isomeric forms in allproportions.

In the context of the invention, “HFO-1234yf” refers to2,3,3,3-tetrafluoropropene,

In the context of the invention, “HFO-1234ye” refers to1,2,3,3-tetrafluoropropene, regardless of whether it is cis (Z) or trans(E). The term “HFO-1234ye” therefore covers cis-HFO-1234ye,trans-HFO-1234ye, and all mixtures of the two isomeric forms in allproportions.

According to one embodiment, hydrofluorocarbon is chosen from the groupconsisting of difluoromethane (HFC-32), pentafluoroethane (HFC-125),1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane(HFC-134a), 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161),1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1-trifluoropropane(HFC-263fb), and mixtures thereof.

According to one embodiment, the refrigerant F according to theinvention comprises at least one tetrafluoropropene (HFO-1234) selectedfrom HFO-1234yf and HFO-1234ze, and at least one hydrofluorocarbonselected from the group consisting of difluoromethane (HFC-32),pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134),1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a),fluoroethane (HFC-161), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea),1,1,1-trifluoropropane (HFC-263fb), and mixtures thereof.

According to one embodiment, the refrigerant F comprises twotetrafluoropropenes, especially HFO-1234yf and HFO-1234ze.

According to specific embodiments, the refrigerant F according to theinvention is a binary composition (consisting of two heat transfercompounds) or ternary (consisting of three heat transfer compounds) orquaternary (consisting of four transfer compounds of heat) orquinternary (consisting of five heat transfer compounds).

Impurities may or may not be present in such refrigerants F. Whenpresent, they may represent less than 1%, preferably less than 0.5%,preferably less than 0.1%, preferably less than 0.05% and preferablyless than 0.01% of said fluid.

According to one embodiment, the refrigerant F essentially consists oftwo, three, four or five heat transfer compounds.

Preferred refrigerant fluid F compositions according to the inventioncomprise, or preferably consist of, the following mixtures:

HFO-1234yf HFC-32 HFO-1234yf HFC-152a HFO-1234yf HFC-134a HFO-1234yfHFC-125 HFO-1234ze HFC-32 HFO-1234ze HFC-152a HFO-1234ze HFC-134aHFO-1234ze HFC-125

Preferred refrigerant fluid F compositions according to the inventioncomprise, or preferably consist of, the following mixtures:

HFO-1234yf HFC-32 HFC-125 HFO-1234yf HFC-152a HFC-125 HFO-1234yfHFC-152a HFC-32 HFO-1234yf HFC-134a HFC-152a HFO-1234yf HFC-134a HFC-32HFO-1234yf HFC-134a HFC-125 HFO-1234ze HFC-134a HFC-152a HFO-1234zeHFC-134a HFC-32 HFO-1234ze HFC-134a HFC-125 HFO-1234ze HFC-152a HFC-32HFO-1234ze HFC-152a HFC-125 HFO-1234ze HFC-32 HFC-125 HFO-1234yfHFO-1234ze HFC-134a HFO-1234yf HFO-1234ze HFC-152a HFO-1234yf HFO-1234zeHFC-134 HFO-1234yf HFO-1234ze HFC-32 HFO-1234yf HFO-1234ze HFC-125

Preferred refrigerant fluid F compositions according to the inventioncomprise, or preferably consist of, the following mixtures:

HFO-1234yf HFC-134a HFC-152a HFC-32 HFO-1234yf HFC-134a HFC-152a HFC-125HFO-1234yf HFO-1234ze HFC-134a HFC-32 HFO-1234yf HFO-1234ze HFC-134aHFC-152a HFO-1234yf HFO-1234ze HFC-134a HFC-125 HFO-1234ze HFC-134aHFC-152a HFC-32 HFO-1234ze HFC-134a HFC-152a HFC-125

Other preferred compositions of refrigerant F according to the inventioncomprise, or preferably consist of, the following mixtures:

HFO-1234yf HFC-134a HFC-152a HFC-125 HFC-32 HFO-1234ze HFC-134a HFC-152aHFC-125 HFC-32

In refrigerant F according to the invention, the weight proportion oftetrafluoropropene(s), and especially of HFO-1234yf and/or HFO-1234ze,can represent, for example, from 1 to 5% of the fluid; or from 5 to 10%of the fluid; or from 10 to 15% of the fluid; or 15 to 20% of the fluid;or from 20 to 25% of the fluid; or 25 to 30% of the fluid; or 30 to 35%of the fluid; or 35 to 40% of the fluid; or 40 to 45% of the fluid; orfrom 45 to 50% of the fluid; or from 50 to 55% of the fluid; or from 55to 60% of the fluid; or from 60 to 65% of the fluid; or from 65 to 70%of the fluid; or from 70 to 75% of the fluid; or from 75 to 80% of thefluid; or from 80 to 85% of the fluid; or from 85 to 90% of the fluid;or from 90 to 95% of the fluid; or from 95 to 99% of the fluid; or from99 to 99.5% of the fluid; or from 99.5 to 99.9% of the fluid; or morethan 99.9% of the fluid, based on the total weight of said fluid. Thecontent of tetrafluoropropene, and especially of HFO-1234yf and/orHFO-1234ze, in the refrigerant F may also vary in several of the aboveranges: for example from 50 to 55% and from 55 to 60%, meaning, 50 to60%, etc.

According to a preferred embodiment, the weight proportion oftetrafluoropropene(s), and in particular of HFO-1234yf and/orHFO-1234ze, in the refrigerant F is greater than 70%, preferably between70% and 95%, preferably between 75% and 90%, and especially between 75%and 78%.

In the refrigerant according to the invention, the weight proportion ofhydrofluorocarbon(s) may represent in particular from 1 to 5% of thefluid; or from 5 to 10% of the fluid; or from 10 to 15% of the fluid; or15 to 20% of the fluid; or from 20 to 25% of the fluid; or 25 to 30% ofthe fluid; or 30 to 35% of the fluid; or 35 to 40% of the fluid; or 40to 45% of the fluid; or from 45 to 50% of the fluid; or from 50 to 55%of the fluid; or from 55 to 60% of the fluid; or from 60 to 65% of thefluid; or from 65 to 70% of the fluid; or from 70 to 75% of the fluid;or from 75 to 80% of the fluid; or from 80 to 85% of the fluid; or from85 to 90% of the fluid; or from 90 to 95% of the fluid; or from 95 to99% of the fluid; or from 99 to 99.5% of the fluid; or 99.5 to 99.9% ofthe fluid, based on the total weight of said fluid. The content ofhydrofluorocarbon(s) in the refrigerant F may also vary in several ofthe above ranges: for example 50 to 55% and 55 to 60%, hence, 50 to 60%,etc.

According to a preferred embodiment, the weight proportion ofhydrofluorocarbon(s) in the refrigerant F is less than 70%, preferablyless than 50%, preferably from 10% to 30%, and especially 18% to 27%, inrelation to the total weight of said fluid.

Preferred compositions of refrigerant F are as follows:

Concentration ranges (weight proportion in %) More Most Preferredpreferred preferred (V/W/ (V/W/ (V/W/ V W X Y Z X/Y/Z) X/Y/Z) X/Y/Z)HFO- HFC-32 60-85/ 63-79/ 64-79/ 1234yf 15-40 37-21 21-36 HFO- HFC-10-95/ 50-95/ 80-95/ 1234yf 152a 5-90 5-50 5-20 HFO- HFC- 10-95/ 40-60/50-60/ 1234yf 134a 5-90 40-60 40-50 HFO- HFC- 10-95/ 50-95/ 80-95/1234yf 125 5-90 5-50 5-20 HFO- HFC-32 10-95/ 10-40/ 25-35/ 1234ze 5-9060-90 65-75 HFO- HFC- 10-95/ 35-95/ 45-95/ 1234ze 152a 5-90 5-65 5-55HFO- HFC- 10-95/ 40-60/ 50-60/ 1234ze 134a 5-90 40-60 40-50 HFO- HFC-10-95/ 50-95/ 80-95/ 1234ze 125 5-90 5-50 5-20 HFO- HFC- HFC- 1-98/1-50-98/1- 56-80/5- 1234y1 134a 152a 98/1-98 49/1-49 22/5-22 HFO- HFC-HFC- 1-98/1- 50-98/1- 56-80/5- 1234ze 134a 152a 98/1-98 49/1-49 22/5-22

The preferred refrigerants F are those comprising the aforementionedmixtures in the amounts mentioned in the table above.

According to one embodiment, the preferred refrigerant compositions areas follows:

-   -   HFO-1234yf and HFC-134a;    -   HFO-1234ze and HFC-134a; and    -   HFO-1234yf and HFC-152a and HFC-134a.

According to one embodiment, the preferred refrigerants comprise thefollowing mixtures:

-   -   HFO-1234yf and HFC-134a;    -   HFO-1234ze and HFC-134a; and    -   HFO-1234yf and HFC-152a and HFC-134a.

According to a preferred embodiment, the refrigerant F is thatcomprising (preferably constituted): from 75.5 to 79.5% weight ofHFO-1234yf, from 12 to 16% weight of HFC-152a, and from 6.5 to 10.5%weight of HFC-134a. In particular, the refrigerant F comprises(preferably consists of) 77.5% weight of HFO-1234yf, 14% weight ofHFC-152a and 8.5% weight of HFC-134a, based on the total weight of saidfluid F.

According to a preferred embodiment, the refrigerant F is thatcomprising (preferably consisting) from 74 to 81.5% weight ofHFO-1234yf, from 6.5 to 10.5% weight of HFC-134a, and from 12 to 16%weight of HFC-152a, based on the total weight of said fluid F.

Azeotropic or quasi-azeotropic mixture can be identified from the liquidand vapour saturations at a given temperature.

Within the scope of the invention, the term “vapour saturation pressure”or “Psat vap”, refers to the pressure at which the first drop of liquidbegins to form in a fluid in vapour state. This pressure is also calledDew pressure.

In the context of the invention, the term “liquid saturation pressure”or “Psat liq”, refers to the pressure at which the first vapour bubblebegins to form in a liquid state fluid. This pressure is also known asbubble pressure.

In the context of the invention, the R_(p) percentage, calculated fromthe vapour and liquid saturation pressures, corresponds to the followingequation:

${Rp} = {\left\lbrack \frac{\left( {{{Psat}\mspace{14mu} {liq}} - {{Psat}\mspace{14mu} {vap}}} \right)}{{Psat}\mspace{14mu} {liq}} \right\rbrack \times 100}$

In the context of the invention, a mixture is considered azeotropic whenthe R_(p) percentage defined above is between 0 and 0.5%.

In the context of the invention, “between x and y” refers to an intervalwherein the x and y terminals are included. For example, the range“between 0 and 0.50%” includes in particular, the values 0 and 0.5%.

In the context of the invention, a mixture is almost azeotropic when theR_(p) percentage defined above is strictly greater than 0.5% andstrictly less than 10.0%.

By way of example and in accordance with ASHRAE STANDARD 34-2013 “Designand safety classification of refrigerants”, the mixtures of the tablebelow are classified as azeotropic, according to this standard (thecomponents, compositions and temperatures are indicated by the samestandard, and the pressures are calculated by Refrop 9 (Reference fluidProperties): Software developed by NIST (National Institute of Standardsand Technology) for the calculation of the properties of refrigerants):

Psat Psat RP Liq vap (value Tem- (bar (bar rounded per- abs) abs) to theCom- weight ature (± (± nearest Product ponents % (° C.) 0.5%) 0.5%)tenth) R500 R12/ 73.8/ 0.0 3.643 3.638 0.1 R152a 26.2 R501 R22/R12 75/25−41.0 0.996 0.992 0.4 R502 R22/ 48.8/ 19.0 9.803 9.800 0.0 R115 51.2R504 R32/ 48.2/ 17.0 15.240 15.229 0.1 R115 51.8 R507A R125/ 50/50 −40.01.386 1.386 0.0 R143a R508A R23/ 39/61 −86.0 1.111 1.111 0.0 R116 R512AR134a/ 5/95 10.0 3.728 3.728 0.0 R152a

This table describes in particular, azeotropically classifiedrefrigerants showing a relative difference in saturation pressures ofless than 0.5%.

Some of the refrigerants F according to the invention, have theadvantage of being azeotropic or quasi-azeotropic. The followingmixtures may especially be mentioned:

Psat Psat RP Liq vap (value Tem- (bar (bar rounded per- abs) abs) to theature (± (± nearest (° C.) 0.5%) 0.5%) tenth) type R1234yf R134a 60.040.0 30.00 8.208 8.208 azeo- trope 56.0 44.0 30.00 8.211 8.211 azeo-trope 50.0 50.0 30.00 8.205 8.204 azeo- trope 45.0 55.0 30.00 8.1918.187 azeo- trope 40.0 60.0 30.00 8.169 8.161 azeo- trope R1234ze R134a58 42.0 30.00 6.830 6.705 quasi- azeo- trope 50 50.0 30.00 6.983 6.870quasi- azeo- trope 45 55.0 30.00 7.072 6.969 quasi- azeo- trope 40 60.030.00 7.157 7.066 1.3 quasi- azeo- trope R1234yf R152a 95.0 5.0 −20.001.512 1.512 0.0 azeo- trope 90.0 10.0 5.00 3.748 3.748 0.0 azeo- trope85.0 15.0 25.00 6.882 6.882 0.0 azeo- trope 80.0 20.0 30.00 7.902 7.9020.0 azeo- trope R1234ze R152a 95 5.0 30.00 5.998 5.947 0.9 quasi- azeo-trope 90 10.0 30.00 6.172 6.097 1.2 quasi- azeo- trope 85 15.0 30.006.314 6.232 1.3 quasi- azeo- trope 80 20.0 30.00 6.431 6.352 1.2 quasi-azeo- trope 75 25.0 30.00 6.528 6.458 1.1 quasi- azeo- trope

RP Psat Psat (value Liq vap round- Tem- (bar (bar ed per- abs) abs) tothe ature (± (± nearest (° C.) 0.5%) 0.5%) tenth) type R1234 R134a R152ayf 81.5 8.5 10.0 30.00 7.972 7.968 0.1 azeo- trope 77.5 8.5 14.0 26.977.319 7.316 0.0 azeo trope 76.5 8.5 15.0 30.00 7.955 7.952 0.0 azeo-trope 71.5 8.5 20.0 30.00 7.928 7.923 0.1 azeo- trope 66.5 8.5 25.030.00 7.894 7.883 0.1 azeo- trope R134a R152a R1234e 2.0 10.0 88.0 30.006.216 6.136 1.3 quasi- azeo- trope 5.0 10.0 85.0 30.00 6.280 6.195 1.4quasi- azeo trope 8.5 10.0 81.5 30.00 6.353 6.263 1.4 quasi- azeo trope2.0 15.0 83.0 30.00 6.352 6.268 1.3 quasi- azeo- trope 5.0 15.0 80.030.00 6.407 6.323 1.3 quasi- azeo- trope 8.5 15.0 76.5 30.00 6.470 6.3851.3 quasi- azeo- trope 2.0 20.0 78.0 30.00 6.464 6.385 1.2 quasi- azeo-trope 5.0 20.0 75.0 30.00 6.511 6.435 1.2 quasi- azeo- trope 8.5 20.071.5 30.00 6.565 6.492 1.1 quasi- azeo- trope

According to a preferred embodiment, refrigerants F comprising(preferably constituted) from 74 to 81.5% weight of HFO-1324yf, from 6.5to 10.5% weight of HFC-134a, and from 12 to 16% weight of HFC-152a, inrelation to the total weight of the composition, are azeotropiccompositions at a temperature between −40.00 and 70.00° C., and at apressure between 0.5 and 21.0 bar abs (±0.5%).

According to a preferred embodiment, refrigerants F comprising(preferably constituted) from 75.5% to 79.5% weight of HFO-1324yf, from6.5 to 10.5% weight of HFC-134a, and from 12 to 16% weight of HFC-152a,in relation to the total weight of the composition, are azeotropiccompositions at a temperature between −40.00 and 70.00° C., and at apressure between 0.5 and 21.0 bar abs (±0.5%).

Preferred refrigerant fluid F constitute the following azeotropiccompositions:

Psat Psat RP Liq vap (value Tem- (bar (bar rounded per- abs) abs) to theature (± (± nearest R1234yf R134a R152a (° C.) 0.5%) 0.5%) tenth) 77.58.5 14.0 −40.00 0.616 0.614 77.5 8.5 14.0 −35.00 0.783 0.781 77.5 8.514.0 −30.00 0.984 0.982 77.5 8.5 14.0 −25.00 1.224 1.221 77.5 8.5 14.0−20.00 1.507 1.504 77.5 8.5 14.0 −15.00 1.838 1.835 77.5 8.5 14.0 −10.002.223 2.221 77.5 8.5 14.0 −5.00 2.668 2.665 77.5 8.5 14.0 0.00 3.1783.176 77.5 8.5 14.0 5.00 3.759 3.757 77.5 8.5 14.0 10.00 4.418 4.41677.5 8.5 14.0 15.00 5.161 5.158 77.5 8.5 14.0 20.00 5.994 5.991 77.5 8.514.0 25.00 6.924 6.921 77.5 8.5 14.0 26.97 7.319 7.316 77.5 8.5 14.030.00 7.959 7.956 77.5 8.5 14.0 35.00 9.106 9.102 77.5 8.5 14.0 40.0010.371 10.367 77.5 8.5 14.0 45.00 11.765 11.760 77.5 8.5 14.0 50.0013.293 13.288 77.5 8.5 14.0 55.00 14.966 14.960 77.5 8.5 14.0 60.0016.793 16.786 77.5 8.5 14.0 65.00 18.783 18.775 77.5 8.5 14.0 70.0020.948 20.938

Preferred refrigerant fluid F constitute the following azeotropiccompositions:

Psat Psat RP Liq vap (value Tem- (bar (bar rounded per- abs) abs) to theature (± (± nearest R1234yf R134a R152a (° C.) 0.5%) 0.5%) tenth) 77.56.5 16.0 −40.00 0.615 0.613 77.5 6.5 16.0 −35.00 0.782 0.779 77.5 6.516.0 −30.00 0.982 0.979 77.5 6.5 16.0 −25.00 1.221 1.218 77.5 6.5 16.0−20.00 1.504 1.501 77.5 6.5 16.0 −15.00 1.834 1.831 77.5 6.5 16.0 −10.002.219 2.216 77.5 6.5 16.0 −5.00 2.663 2.660 77.5 6.5 16.0 0.00 3.1723.169 77.5 6.5 16.0 5.00 3.752 3.749 77.5 6.5 16.0 10.00 4.409 4.40677.5 6.5 16.0 15.00 5.150 5.147 77.5 6.5 16.0 20.00 5.981 5.979 77.5 6.516.0 25.00 6.910 6.907 77.5 6.5 16.0 26.97 7.304 7.301 77.5 6.5 16.030.00 7.942 7.939 77.5 6.5 16.0 35.00 9.086 9.083 77.5 6.5 16.0 40.0010.349 10.346 77.5 6.5 16.0 45.00 11.740 11.736 77.5 6.5 16.0 50.0013.265 13.261 77.5 6.5 16.0 55.00 14.935 14.930 77.5 6.5 16.0 60.0016.757 16.752 77.5 6.5 16.0 65.00 18.743 18.737 77.5 6.5 16.0 70.0020.903 20.897

Preferred refrigerant fluid F constitute the following azeotropiccompositions:

Psat Psat RP Liq vap (value Tem- (bar (bar rounded per- abs) abs) to theature (± (± nearest R1234yf R134a R152a (° C.) 0.5%) 0.5%) tenth) 81.56.5 12.0 −40.00 0.619 0.618 81.5 6.5 12.0 −35.00 0.787 0.785 81.5 6.512.0 −30.00 0.988 0.986 81.5 6.5 12.0 −25.00 1.228 1.226 81.5 6.5 12.0−20.00 1.511 1.509 81.5 6.5 12.0 −15.00 1.842 1.841 81.5 6.5 12.0 −10.002.228 2.226 81.5 6.5 12.0 −5.00 2.672 2.671 81.5 6.5 12.0 0.00 3.1823.181 81.5 6.5 12.0 5.00 3.763 3.761 81.5 6.5 12.0 10.00 4.420 4.41981.5 6.5 12.0 15.00 5.162 5.160 81.5 6.5 12.0 20.00 5.993 5.991 81.5 6.512.0 25.00 6.922 6.919 81.5 6.5 12.0 26.97 7.316 7.313 81.5 6.5 12.030.00 7.954 7.951 81.5 6.5 12.0 35.00 9.097 9.094 81.5 6.5 12.0 40.0010.359 10.355 81.5 6.5 12.0 45.00 11.748 11.743 81.5 6.5 12.0 50.0013.272 13.266 81.5 6.5 12.0 55.00 14.939 14.932 81.5 6.5 12.0 60.0016.759 16.751 81.5 6.5 12.0 65.00 18.742 18.732 81.5 6.5 12.0 70.0020.898 20.887

Preferred refrigerant fluid F constitute the following azeotropiccompositions:

RP Psat Psat (value Liq vap round- Tem- (bar (bar ed per- abs) abs) tothe R1234 ature (± (± nearest yf R134a R152a (° C.) 0.5%) 0.5%) tenth)75.5 10.0 14.5 −40.00 0.615 0.612 75.5 10.0 14.5 −35.00 0.782 0.778 75.510.0 14.5 −30.00 0.983 0.979 75.5 10.0 14.5 −25.00 1.222 1.218 75.5 10.014.5 −20.00 1.505 1.501 75.5 10.0 14.5 −15.00 1.836 1.833 75.5 10.0 14.5−10.00 2.222 2.218 75.5 10.0 14.5 −5.00 2.667 2.663 75.5 10.0 14.5 0.003.177 3.173 75.5 10.0 14.5 5.00 3.759 3.755 75.5 10.0 14.5 10.00 4.4184.415 75.5 10.0 14.5 15.00 5.161 5.158 75.5 10.0 14.5 20.00 5.995 5.99275.5 10.0 14.5 25.00 6.927 6.923 75.5 10.0 14.5 26.97 7.323 7.319 75.510.0 14.5 30.00 7.963 7.960 75.5 10.0 14.5 35.00 9.112 9.108 75.5 10.014.5 40.00 10.380 10.375 75.5 10.0 14.5 45.00 11.775 11.770 75.5 10.014.5 50.00 13.307 13.301 75.5 10.0 14.5 55.00 14.983 14.977 75.5 10.014.5 60.00 16.814 16.806 75.5 10.0 14.5 65.00 18.808 18.800 75.5 10.014.5 70.00 20.978 20.968

Preferred refrigerant fluid F constitute the following azeotropiccompositions:

Psat Psat RP Liq yap (value Tem- (bar (bar rounded per- abs) abs) to theature (± (± nearest R1234yf R134a R152a (° C.) 0.5%) 0.5%) tenth) 77.510.5 12.0 −40.00 0.618 0.615 77.5 10.5 12.0 −35.00 0.785 0.783 77.5 10.512.0 −30.00 0.987 0.984 77.5 10.5 12.0 −25.00 1.227 1.224 77.5 10.5 12.0−20.00 1.510 1.508 77.5 10.5 12.0 −15.00 1.842 1.840 77.5 10.5 12.0−10.00 2.229 2.226 77.5 10.5 12.0 −5.00 2.674 2.672 77.5 10.5 12.0 0.003.186 3.183 77.5 10.5 12.0 5.00 3.768 3.766 77.5 10.5 12.0 10.00 4.4294.426 77.5 10.5 12.0 15.00 5.173 5.170 77.5 10.5 12.0 20.00 6.008 6.00577.5 10.5 12.0 25.00 6.940 6.937 77.5 10.5 12.0 26.97 7.336 7.332 77.510.5 12.0 30.00 7.978 7.974 77.5 10.5 12.0 35.00 9.127 9.122 77.5 10.512.0 40.00 10.395 10.390 77.5 10.5 12.0 45.00 11.791 11.785 77.5 10.512.0 50.00 13.324 13.316 77.5 10.5 12.0 55.00 15.000 14.992 77.5 10.512.0 60.00 16.831 16.821 77.5 10.5 12.0 65.00 18.826 18.815 77.5 10.512.0 70.00 20.996 20.983

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 14% (±0.2%) weight of HFC-152a and 8.5%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of between −40.00°C. and 70.00° C. at a pressure of between 0.5 and 21.0 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 14% (±0.2%) weight of HFC-152a and 8.5%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of 26.97° C.(±0.50° C.) at a pressure of 7.3 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%weight of HFO-1234yf, 16% weight of HFC-152a and 6.5% weight ofHFC-134a, in relation to the total weight of the composition, saidcomposition having a boiling point between −40.00° C. and 70.00° C., ata pressure of between 0.5 and 21.0 bar abs (±0.5%), and preferablybetween 0.6 and 20.9 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%weight of HFO-1234yf, 16% weight of HFC-152a and 6.5% weight ofHFC-134a, in relation to the total weight of the composition, saidcomposition having a boiling temperature of 26.97° C. (±0.50° C.) at apressure of 7.3 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 15.8% (±0.2%) weight of HFC-152a and 6.7%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point between −40.00° C.and 70.00° C., at a pressure between 0.5 and 21.0 bar abs (±0.5%), andpreferably between 0.6 and 20.9 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 15.8% (±0.2%) weight of HFC-152a and 6.7%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of 26.97° C.(±0.50° C.) at a pressure of 7.3 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 81.5%(±0.2%) weight of HFO-1234yf, 12% (±0.2%) weight of HFC-152a and 6.5%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point between −40.00° C.and 70.00° C., at a pressure between 0.5 and 21.0 bar abs (±0.5%), andpreferably between 0.6 and 20.9 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 81.5%(±0.2%) weight of HFO-1234yf, 12% (±0.2%) weight of HFC-152a and 6.5%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of 26.97° C.(±0.50° C.) at a pressure of 7.3 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 75.5%(±0.2%) weight of HFO-1234yf, 14.5% (±0.2%) weight of HFC-152a and 10%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point between −40.00° C.and 70.00° C., at a pressure between 0.5 and 21.0 bar abs (±0.5%), andpreferably between 0.78 and 20.98 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 75.5%(±0.2%) weight of HFO-1234yf, 14.5% (±0.2%) weight of HFC-152a and 10%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of 26.97° C.(±0.50° C.) at a pressure of 7.3 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 12% (±0.2%) weight of HFC-152a and 10.5%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition with a boiling point between −40.00° C.and 70.00° C., at a pressure between 0.5 and 21.0 bar abs (±0.5%), andpreferably between 0.61 and 21.00 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 12% (±0.2%) weight of HFC-152a and 10.5%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of 26.97° C.(±0.50° C.) at a pressure of 7.3 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 12.2% (±0.2%) weight of HFC-152a and 10.3%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition with a boiling point between −40.00° C.and 70.00° C., at a pressure between 0.5 and 21.0 bar abs (±0.5%), andpreferably between 0.61 and 21.00 bar abs (±0.5%).

According to a preferred embodiment, the azeotropic compositionaccording to the invention comprises (preferably consists of) 77.5%(±0.2%) weight of HFO-1234yf, 12.2% (±0.2%) weight of HFC-152a and 10.3%(±0.2%) weight of HFC-134a, in relation to the total weight of thecomposition, said composition having a boiling point of 26.97° C.(±0.50° C.) at a pressure of 7.3 bar abs (±0.5%).

Lubricant

In the context of the invention, the terms “lubricant”, “lubricant oil”and “lubricating oil” are used interchangeably.

According to the invention, the lubricant may comprise one or morepolyol esters.

According to one embodiment, the polyol esters are obtained by reactionof at least one polyol with a carboxylic acid or with a mixture ofcarboxylic acids.

In the context of the invention, and unless otherwise indicated, theterm “polyol” means a compound containing at least two hydroxyl groups(—OH).

Polyol Esters A)

According to one embodiment, the polyol esters according to theinvention have the following formula (I):

R¹[OC(O)R²]_(n)   (I)

wherein:

-   -   R¹ is a linear or branched hydrocarbon radical, optionally        substituted with at least one hydroxyl group and/or comprising        at least one heteroatom selected from the group consisting of        —O—, —N—, and —S—;    -   each R² is, independently of each other, selected from the group        consisting of:        -   i) H;        -   ii) an aliphatic hydrocarbon radical;        -   iii) a branched hydrocarbon radical;        -   iv) a mixture of a radical ii) and/or iii) with an aliphatic            hydrocarbon radical comprising from 8 to 14 carbon atoms;            and    -   n is an integer of at least 2.

In the context of the invention, the term “hydrocarbon radical” means aradical composed of carbon atoms and hydrogen.

According to one embodiment, the polyols have the following generalformula (II):

R¹(OH)_(n)   (II)

wherein:

-   -   R¹ is a linear or branched hydrocarbon radical, optionally        substituted with at least one hydroxyl group, preferably with        two hydroxyl groups, and/or comprising at least one heteroatom        selected from the group consisting of —O—, —N—, and —S—; and    -   n is an integer of at least 2.

Preferably, R¹ is a hydrocarbon, linear or branched radical, comprisingfrom 4 to 40 carbon atoms, preferably from 4 to 20 carbon atoms.

Preferably, R¹ is a hydrocarbon, linear or branched radical comprisingat least one oxygen atom.

Preferably, R¹ is a branched hydrocarbon radical comprising from 4 to 10carbon atoms, preferably 5 carbon atoms, substituted by two hydroxylgroups.

According to a preferred embodiment, the polyols comprise from 2 to 10hydroxyl groups, preferably from 2 to 6 hydroxyl groups.

The polyols according to the invention may comprise one or moreoxyalkylene groups, in this particular case polyether polyols.

The polyols according to the invention may also comprise one or morenitrogen atoms. For example, the polyols may be alkanol aminescontaining from 3 to 6 OH groups. Preferably, the polyols are alkanolamines containing at least two OH groups, and preferably at least three.

According to the present invention, the preferred polyols are selectedfrom the group consisting of ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, dipropylene glycol, glycerol,neopentyl glycol, 1,2-butanediol, 1,4-butanediol, 1,3-butanediol,pentaerythritol, dipentaerythritol, tripentaerythritol, triglycerol,trimethylolpropane, sorbitol, hexaglycerol, and mixtures thereof.

According to the invention, carboxylic acids can satisfy the followinggeneral formula (III):

R²COOH   (III)

wherein:

-   -   R² is selected from the group consisting of:        -   i) H;        -   ii) an aliphatic hydrocarbon radical;        -   iii) a branched hydrocarbon radical;        -   iv) a mixture of a radical ii) and/or iii), with an            aliphatic hydrocarbon radical comprising from 8 to 14 carbon            atoms.

Preferably, R² is an aliphatic hydrocarbon radical comprising from 1 to10, preferably from 1 to 7 carbon atoms, and especially from 1 to 6carbon atoms.

Preferably, R² is a branched hydrocarbon radical comprising from 4 to 20carbon atoms, especially from 5 to 14 carbon atoms, and preferably from6 to 8 carbon atoms.

According to a preferred embodiment, a branched hydrocarbon radical hasthe following formula (IV):

—C(R³)R⁴)(R⁵)   (IV)

wherein R³, R⁴ and R⁵ are, independently of each other, an alkyl group,and at least one of the alkyl groups contains at least two carbon atoms.Such branched alkyl groups, once bound to the carboxyl group, are knownas “neo group”, and the corresponding acid as “neo acid”. Preferably, R³and R⁴ are methyl groups and R¹⁰ is an alkyl group comprising at leasttwo carbon atoms.

According to the invention, the R² radical may comprise one or morecarboxy groups, or ester groups such as —COOR⁶, with R⁶ representing analkyl radical, hydroxyalkyl radical or a hydroxyalkyloxy alkyl group.

Preferably, the acid R²COOH of formula (III) is a monocarboxylic acid.

Examples of carboxylic acids in which the hydrocarbon radical isaliphatic include: formic acid, acetic acid, propionic acid, butyricacid, pentanoic acid, hexanoic acid and heptanoic acid.

Examples of carboxylic acids among which the hydrocarbon-basedesterified radical include: 2-ethyl-n-butyric acid, 2-hexyldecanoicacid, isostearic acid, 2-methyl-hexanoic acid, 2-methylbutanoic acid,3-methylbutanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethylhexanoicacid, neoheptanoic acid, and neodecanoic acid.

The third type of carboxylic acids which can be used in the preparationof the polyol esters of formula (I) are carboxylic acids comprising analiphatic hydrocarbon radical containing from 8 to 14 carbon atoms. Forexample: decanoic acid, dodecanoic acid, lauric acid, stearic acid,myristic acid, behenic acid, etc. Examples of dicarboxylic acids,include maleic acid, succinic acid, adipic acid, sebacic acid.

According to a preferred embodiment, the carboxylic acids used toprepare the polyol esters of formula (I) comprise a mixture ofmonocarboxylic and dicarboxylic acids, the proportion of monocarboxylicacids being the majority. The presence of dicarboxylic acids resultsespecially in the formation of polyol esters of high viscosity.

In particular, the polyol ester-forming reaction of formula (I) byreaction between the carboxylic acid and the polyols is anacid-catalysed reaction. This is mostly a reversible reaction, which canbe complete by using a large amount of acid or by removing the waterformed during the reaction.

The esterification reaction can be carried out in the presence oforganic or inorganic acids, such as sulphuric acid, phosphoric acid.

Preferably, the reaction is carried out in the absence of a catalyst.

The amount of carboxylic acid and polyol in the mixture may varydepending on the desired results. In the particular case where all thehydroxyl groups are esterified, a sufficient amount of carboxylic acidmust be added to react with all the hydroxyls.

According to one embodiment, when using mixtures of carboxylic acids,these can react sequentially with the polyols.

According to a preferred embodiment, when using a mixture of carboxylicacids, a polyol reacts first with a carboxylic acid, typically thehighest molecular weight carboxylic acid, followed by reaction with thecarboxylic acid with an aliphatic hydrocarbon chain.

According to one embodiment, the esters can be formed by reactionbetween the carboxylic acids (or their anhydride or ester derivatives)with the polyols, in the presence of acids at high temperature, whileremoving the water formed during the reaction. Typically, the reactioncan be carried out at a temperature of 75 to 200° C.

According to another embodiment, the polyol esters formed may compriseunreactive hydroxyl groups, in this case they are esters of partiallyesterified polyols.

According to a preferred embodiment, the polyol esters are obtained frompentaerythritol alcohol, and from a mixture of carboxylic acids:isononanoic acid, at least one acid having an aliphatic hydrocarbonradical comprising from 8 to 10 carbon atoms, and heptanoic acid. Thepreferred polyol esters are obtained from pentaerythritol, and a mixtureof 70% of isononanoic acid, 15% of at least one carboxylic acid with analiphatic hydrocarbon radical comprising from 8 to 10 carbon atoms, and15% heptanoic acid. For example, Solest 68 oil sold by CPI EngineeringServices Inc.

Polyol Esters B)

According to another embodiment, the polyol esters of the inventioncomprise at least one ester of one or more branched carboxylic acidscomprising at most 8 carbon atoms. The ester is mostly obtained byreacting said branched carboxylic acid with one or more polyols.

Preferably, the branched carboxylic acid comprises at least 5 carbonatoms. In particular, the branched carboxylic acid comprises from 5 to 8carbon atoms, and preferably contains 5 carbon atoms.

Preferably, the above-mentioned branched carboxylic acid does notcomprise 9 carbon atoms. In particular, said carboxylic acid is not3,5,5-trimethylhexanoic acid.

According to a preferred embodiment, the branched carboxylic acid isselected from 2-methylbutanoic acid, 3-methylbutanoic acid, and mixturesthereof.

In a preferred embodiment, the polyol is selected from the groupconsisting of neopentyl glycol, glycerol, trimethylol propane,pentaerythritol, dipentaerythritol, tripentaerythritol, and mixturesthereof.

According to a preferred embodiment, the polyol esters are obtainedfrom:

-   -   i) a carboxylic acid selected from 2-methylbutanoic acid,        3-methylbutanoic acid, and mixtures thereof; and    -   ii) a polyol selected from the group consisting of neopentyl        glycol, glycerol, trimethylolpropane, pentaerythritol,        dipentaerythritol, tripentaerythritol, and mixtures thereof.

Preferably, the polyol ester is that obtained from 2-methylbutanoic acidand pentaerythritol.

Preferably, the polyol ester is that obtained from 2-methylbutanoic acidand dipentaerythritol.

Preferably, the polyol ester is that obtained from 3-methylbutanoic acidand pentaerythritol.

Preferably, the polyol ester is that obtained from 3-methylbutanoic acidand dipentaerythritol.

Preferably, the polyol ester is that obtained from 2-methylbutanoic acidand neopentyl glycol.

Polyol Esters C)

According to another embodiment, the polyol esters according to theinvention are poly (neopentylpolyol) esters obtained by:

-   -   i) reaction of a neopentylpolyol with the following formula (V):

wherein:

-   -   each R represents, independently of each other, CH₃, C₂H₅ or        CH₂OH;    -   p is an integer between 1 and 4;    -   with at least one monocarboxylic acid containing 2 to 15 carbon        atoms, and in the presence of an acid catalyst, the molar ratio        between the carboxyl groups and the hydroxyl groups being less        than 1:1, to form a composition of partially esterified poly        (neopentyl) polyol; and    -   ii) reacting the partially esterified poly (neopentyl) polyol        composition obtained at the end of step i) with another        carboxylic acid having from 2 to 15 carbon atoms, to form the        final composition of poly (neopentyl polyol) ester(s).

Preferably, reaction i) is carried out with a molar ratio ranging from1:4 to 1:2.

Preferably, neopentyl polyol has the following formula (VI):

wherein each R is, independently of each other, CH₃, C₂H₅ or CH₂OH.

Preferred neopentyl polyols are those selected from pentaerythritol,dipentaerythritol, tripentaerythritol, tetraerythritol,trimethylolpropane, trimethylolethane, and neopentyl glycol. Inparticular, the neopentyl polyol is pentaerythritol.

Preferably, a single neopentyl polyol is used to produce the POE-basedlubricant. In some cases, two or more neopentyl polyols are used. Thisis particularly the case when a commercial product of pentaerythritolincludes small amounts of dipentaerythritol, tripentaerythritol, andtetraerythritol.

According to a preferred embodiment, the above mentioned monocarboxylicacid comprises from 5 to 11 carbon atoms, preferably from 6 to 10 carbonatoms.

Monocarboxylic acids have in particular, the following general formula(VII):

R′C(O)OH   (VII)

in which R′ is a linear or branched C1-C12 alkyl radical, a C6-C12 arylradical or a C6-C30 aralkyl radical. Preferably, R′ is a C4-C10 alkylradical, and preferentially a C5-C9 alkyl radical.

In particular, the monocarboxylic acid is selected from the groupconsisting of butanoic acid, pentanoic acid, hexanoic acid, heptanoicacid, n-octanoic acid, n-nonanoic acid, n-decanoic acid,3-methylbutanoic acid, 2-methylbutanoic acid, 2,4-dimethylpentanoicacid, 2-ethylhexanoic acid, 3,3,5-trimethylhexanoic acid, benzoic acid,and mixtures thereof.

According to a preferred embodiment, the monocarboxylic acid isn-heptanoic acid, or a mixture of n-heptanoic acid with another linearmonocarboxylic acid, in particular n-octanoic acid and/or n-decanoicacid. Such a mixture of monocarboxylic acid may comprise between 15 and100 mol % of heptanoic acid and between 85 and 0 mol % of othermonocarboxylic acid(s). In particular, the mixture comprises between 75and 100 mol % of heptanoic acid, and between 25 and 0 mol % of a mixtureof octanoic acid and decanoic acid in a molar ratio 3:2.

According to a preferred embodiment, polyol esters comprise:

-   -   i) from 45% to 55% weight of a monopentaerythritol ester with at        least one monocarboxylic acid having from 2 to 15 carbon atoms;    -   ii) less than 13% weight of a dipentaerythritol ester with at        least one monocarboxylic acid having from 2 to 15 carbon atoms;    -   iii) less than 10% weight of a tripentaerythritol ester with at        least one monocarboxylic acid having 2 to 15 carbon atoms; and    -   iv) at least 25% weight of a tetraerythritol ester and other        pentaerythritol oligomers, with at least one monocarboxylic acid        having from 2 to 15 carbon atoms.

Polyol Esters D)

According to another embodiment, the polyol esters according to theinvention have the following formula (VIII):

wherein:

-   -   R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are, independently of each other, H        or CH₃;    -   a, b, c, y, x and z are, independently of each other, an        integer;    -   a+x, b+y, and c+z are, independently of each other, integers        ranging from 1 to 20;    -   R¹³, R¹⁴ and R¹⁵ are, independently of each other, selected from        the group consisting of aliphatic or branched alkyls, alkenyls,        cycloalkyls, aryls, alkylaryls, arylalkyls, alkylcycloalkyls,        cycloalkylalkyls, arylcycloalkyls, cycloalkylaryls,        alkylcycloalkylaryls, alkylarylcycloalkyls,        arylcycloalkylalkyls, arylalkylcycloalkyls, cycloalkylalkylaryls        and cycloalkylarylalkyls,    -   R¹³, R¹⁴ and R¹⁵, consisting 1 to 17 carbon atoms, and may be        optionally substituted.

According to a preferred embodiment, R¹³, R¹⁴ and R¹⁵ each represents,independently of each other, a linear or branched alkyl group, analkenyl group, a cycloalkyl group, said alkyl, alkenyl or cycloalkylgroups may comprise at least one heteroatom selected from N, O, Si, F orS. Preferably, R¹³, R¹⁴ and R¹⁵ have, each independently of each other,from 3 to 8 carbon atoms, preferably from 5 to 7 carbon atoms.

Preferably, a+x, b+y, and c+z are, independently of one another,integers ranging from 1 to 10, preferably from 2 to 8, and even morepreferably from 2 to 4.

Preferably, R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² represent H.

The polyol esters of formula (VIII) above can typically be prepared asdescribed in paragraphs [0027] to [0030] of international applicationWO2012/177742.

In particular, the polyol esters of formula (VIII) are obtained byesterification of glycerol alkoxylates (as described in paragraph [0027]of WO2012/177742) with one or more monocarboxylic acids having from 2 to18 carbon atoms.

According to a preferred embodiment, the monocarboxylic acids have oneof the following formulas:

R¹³COOH

R¹⁴COOH and

R¹⁵COOH

wherein R¹³, R¹⁴ and R¹⁵ are as defined above. Derivatives of thecarboxylic acids can also be used, such as anhydrides, esters and acylhalides.

Esterification can be carried out with one or more monocarboxylic acids.Preferred monocarboxylic acids are those selected from the groupconsisting of acetic acid, propanoic acid, butyric acid, isobutanoicacid, pivalic acid, pentanoic acid, isopentanoic acid, hexanoic acid,heptanoic acid, octanoic acid, 2-ethylhexanoic acid,3,3,5-trimethylhexanoic acid, nonanoic acid, decanoic acid, neodecanoicacid, undecanoic acid, dodecanoic acid, tridecanoic acid, myristic acid,pentadecanoic acid, palmitic acid, stearic acid, oleic acid, linoleicacid, palmitoleic acid, citronellic acid, undecenoic acid, lauric acid,undecylenic acid, linolenic acid, arachidic acid, behenic acid,tetrahydrobenzoic acid, hydrogenated or non-hydrogenated abietic acid,2-ethylhexanoic acid, furoic acid, benzoic acid, 4-acetylbenzoic acid,pyruvic acid, 4-tert-butyl-benzoic acid, naphthenic acid, 2-methylbenzoic acid, salicylic acid, their isomers, their methyl esters, andmixtures thereof.

Preferably, the esterification is carried out with one or moremonocarboxylic acids selected from the group consisting of pentanoicacid, 2-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid,3,3,5-trimethylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid,n-nonanoic acid and isononanoic acid.

Preferably, the esterification is carried out with one or moremonocarboxylic acids selected from the group consisting of butyric acid,isobutyric acid, n-pentanoic acid, 2-methylbutanoic acid,3-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoicacid, 2-ethylhexanoic acid, 3,3,5-trimethylhexanoic acid, n-nonanoicacid, decanoic acid, undecanoic acid, undecylenic acid, lauric acid,stearic acid, isostearic acid, and mixtures thereof.

According to another embodiment, the polyol esters according to theinvention have the following formula (IX):

wherein:

-   -   each of R¹⁷ and R¹⁸, is, independently of each other, H or CH₃;    -   each of m and n is, independently of each other, an integer,        with m+n being an integer from 1 to 10;    -   R¹⁶ and R¹⁹ are, independently of each other, selected from the        group consisting of aliphatic or branched aliphatic or branched        alkyls, alkenyls, cycloalkyls, aryls, alkylaryls, arylalkyls,        alkylcycloalkyls, cycloalkylalkyls, arylcycloalkyls,        cycloalkylaryls, alkylcycloalkylaryls, alkylarylcycloalkyls,        arylcycloalkylalkyls, arylalkylcycloalkyls, cycloalkylalkylaryls        and cycloalkylarylalkyls,    -   R¹⁶ and R¹⁹, consisting 1 to 17 carbon atoms, and may be        optionally substituted.

According to a preferred embodiment, each of R¹⁶ and R¹⁹ eachrepresents, independently of one another, a linear or branched alkylgroup, an alkenyl group, a cycloalkyl group, said alkyl, alkenyl orcycloalkyl groups may comprise at least one heteroatom selected from N,O, Si, F or S Preferably, each of R¹⁶ and R¹⁹ has, independently of eachother, from 3 to 8 carbon atoms, preferably from 5 to 7 carbon atoms.

According to a preferred embodiment, R¹⁷ and R¹⁸ each represents H,and/or m+n is an integer ranging from 2 to 8, from 4 to 10, from 2 to 5,or from 3 to 5. In particular, m+n is 2, 3 or 4.

According to a preferred embodiment, the polyol esters of formula (IX)above are triethylene glycol diesters, tetraethylene glycol diesters, inparticular with one or two monocarboxylic acids having from 4 to 9carbon atoms.

The polyol esters of formula (IX) above may be prepared byesterifications of an ethylene glycol, a propylene glycol, or an oligo-or polyalkylene glycol, (which may be an oligo- or polyethylene glycol,oligo- or polypropylene glycol, or an ethylene glycol-propylene glycolblock copolymer), with one or two monocarboxylic acids comprising 2 to18 carbon atoms. The esterification can be carried out identically tothe esterification reaction used to prepare the polyol esters of formula(VIII) above.

In particular, monocarboxylic acids identical to those used to preparethe polyol esters of formula (VIII) above can be used to form the polyolesters of formula (IX).

According to one embodiment, the lubricant based on polyol estersaccording to the invention comprises from 20 to 80%, preferably from 30to 70%, and preferably from 40 to 60% weight of at least one polyolester of formula (VIII), and from 80 to 20%, preferably from 70 to 30%,and preferably from 60 to 40% weight of at least one polyol ester offormula (IX).

In general, certain alcohol functional groups cannot be esterifiedduring the esterification reaction, however, their proportion remainslow. Thus, the POE can comprise between 0 and 5% relative molar ratio ofCH₂OH in relation to —CH₂—O—C(═O)—.

Preferred POE lubricants according to the invention are those having aviscosity between 1 to 1000 centiStokes (cSt) at 40° C., preferably from10 to 200 cSt, even more preferably from 20 to 100 cSt, andadvantageously from 30 to 80 cSt.

The international classification of oils is provided by ISO3448-1992 (NFT60-141) and according to which oils are designated by their averageviscosity class measured at a temperature of 40° C.

Composition

In the composition of the invention, the weight proportion ofrefrigerant F can represent especially, from 1 to 5% of the composition;or from 5 to 10% of the composition; or from 10 to 15% of thecomposition; or from 15 to 20% of the composition; or from 20 to 25% ofthe composition; or from 25 to 30% of the composition; or from 30 to 35%of the composition; or from 35 to 40% of the composition; or from 40 to45% of the composition; or from 45 to 50% of the composition; or from 50to 55% of the composition; or from 55 to 60% of the composition; or from60 to 65% of the composition; or from 65 to 70% of the composition; orfrom 70 to 75% of the composition; or from 75 to 80% of the composition;or from 80 to 85% of the composition; or from 85 to 90% of thecomposition; or from 90 to 95% of the composition; or from 95 to 99% ofthe composition; or from 99 to 99.5% of the composition; or from 99.5 to99.9% of the composition; or more than 99.9% of the composition. Thecontent of hydrofluorocarbon(s) in the refrigerant F may also vary inseveral of the above ranges: for example 50 to 55% and 55 to 60%, hence,50 to 60%, etc.

According to a preferred embodiment, the composition of the inventioncomprises more than 50% weight of refrigerant F, and in particular from50% to 99% in weight, relative to the total weight of the composition.

In the composition of the invention, the weight proportion of lubricantbased on polyol esters (POE) can represent especially, from 1 to 5% ofthe composition; or from 5 to 10% of the composition; or from 10 to 15%of the composition; or from 15 to 20% of the composition; or from 20 to25% of the composition; or from 25 to 30% of the composition; or from 30to 35% of the composition; or from 35 to 40% of the composition; or from40 to 45% of the composition; or from 45 to 50% of the composition; orfrom 50 to 55% of the composition; or from 55 to 60% of the composition;or from 60 to 65% of the composition; or from 65 to 70% of thecomposition; or from 70 to 75% of the composition; or from 75 to 80% ofthe composition; or from 80 to 85% of the composition; or from 85 to 90%of the composition; or from 90 to 95% of the composition; or from 95 to99% of the composition; or from 99 to 99.5% of the composition; or from99.5 to 99.9% of the composition; or more than 99.9% of the composition.The lubricant content may also vary in several of the above ranges: forexample from 50 to 55%, and from 55 to 60%, meaning from 50 to 60%, etc.

According to one embodiment, the composition according to the inventioncomprises:

-   -   a refrigerant F selected from the group consisting of:    -   HFO-1234yf/HFC-134a;    -   HFO-1234ze/HFC-134a; and    -   HFO-1234yf/HFC-134a/HFC-152a;

and

-   -   at least one lubricant based on polyol esters (POE), especially        selected from polyol esters A), B), C) or D) described above,        especially polyol esters of formulas (I), (VIII) or (XI).

According to one embodiment, the composition according to the inventioncomprises:

-   -   a refrigerant F comprising one of the following mixtures:    -   HFO-1234yf/HFC-134a;    -   HFO-1234ze/HFC-134a; or    -   HFO-1234yf/HFC-134a/HFC-152a;

and

-   -   at least one lubricant based on polyol esters (POE), especially        selected from polyol esters A), B), C) or D) described above,        especially polyol esters of formulas (I), (VIII) or (XI).

According to one embodiment, the composition according to the inventioncomprises:

-   -   a refrigerant F comprising (preferably consisting of) the        mixture HFO-1234yf/HFC-134a/HFC-152a, in particular comprising        from 75.5 to 79.5% weight of HFO-1234yf, from 12 to 16% weight        of HFC-152a, and from 6.5 to 10.5% weight of HFC-134a, and        preferably comprising 77.5% weight of HFO-1234yf, 14% weight of        HFC-152a and 8.5% weight of HFC-134a

and

-   -   at least one lubricant based on polyol esters (POE), especially        selected from polyol esters A), B), C) or D) described above,        especially polyol esters of formulas (I), (VIII) or (XI).

The composition according to the invention may comprise one or moreadditives (which are essentially not heat transfer compounds for theintended application).

The additives may especially be selected from nanoparticles,stabilizers, surfactants, tracer agents, fluorescent agents, odorantsand solubility agents.

Preferably, the additives are not lubricants.

According to one embodiment, the composition of the invention is a heattransfer composition.

The stabilizer(s), when present, preferably represent at most 5% weightin the heat transfer composition. Examples of the stabilizers, includein particular, nitromethane, ascorbic acid, terephthalic acid, azolessuch as tolutriazole or benzotriazole, phenol compounds such astocopherol, hydroquinone, t-butyl hydroquinone,2,6-di-tert-butyl-4-methylphenol, epoxides (optionally fluorinated orperfluorinated alkyl or alkenyl or aromatic) such as n-butyl glycidylether, hexanediol diglycidyl ether, allyl glycidyl ether,butylphenylglycidyl ether, phosphites, phosphonates, thiols andlactones.

As nanoparticles, it is possible to use nanoparticles of carbon, metaloxides (copper, aluminium), TiO₂, Al₂O₃, MoS₂.

Examples of (detectable) tracer agents include deuterated ornon-deuterated hydrofluorocarbons, deuterated hydrocarbons,perfluorocarbons, fluoroethers, brominated compounds, iodinatedcompounds, alcohols, aldehydes, ketones, nitrous oxide and combinationsthereof. The tracer agent is different from the one or more heattransfer compounds that constitute the heat transfer fluid (refrigerantF).

Examples of solubility agents, include hydrocarbons, dimethyl ether,polyoxyalkylene ethers, amides, ketones, nitriles, chlorocarbons,esters, lactones, aryl ethers, fluoroethers and 1,1,1-trifluoroalcanes.The solubility agent is different from the one or more heat transfercompounds composing the heat transfer fluid (refrigerant F).

Examples of fluorescent agents include naphthalimides, perylenes,coumarins, anthracenes, phenanthracenes, xanthenes, thioxanthenes,naphthoxanhthenes, fluoresceins and derivatives and combinationsthereof.

Examples of odorants include alkyl acrylates, allyl acrylates, acrylicacids, acrylesters, alkyl ethers, alkyl esters, alkynes, aldehydes,thiols, thioethers, disulphides, allyl isothiocyanates and alkanoicacids, amines, norbornenes, norbornene derivatives, cyclohexene,heterocyclic aromatic compounds, ascaridole, o-methoxy (methyl) phenoland combinations thereof.

“Heat transfer compound”, respectively “heat transfer fluid” or“refrigerant” refers to a compound, respectively a fluid, capable ofabsorbing heat by evaporating at low temperature and low pressure and ofrejecting heat by condensing at high temperature and high pressure, in avapour compression circuit. In general, a heat transfer fluid maycomprise one, two, three or more than three heat transfer compounds. Inparticular, the refrigerant F is a heat transfer fluid.

“Heat transfer composition” refers to a composition comprising a heattransfer fluid and optionally one or more additives that are not heattransfer compounds for the intended application. In particular, thecomposition according to the invention is a heat transfer composition.

Uses

The present invention also relates to a heat transfer method based onthe use of a heat transfer system containing a vapour compressioncircuit which comprises the composition of the invention as a heattransfer composition, said circuit comprising an oil separator. The heattransfer process may be a method of heating or cooling a fluid or abody.

The invention also relates to the use of the composition described aboveas a heat transfer fluid in a vapour compression system comprising anoil separator, preferably said vapour compression system comprising ascrew compressor.

According to one embodiment, the vapour compression system constitutes:

-   -   an air conditioning system; or    -   a refrigeration system; or    -   a freezing system; or    -   a heat pump system.

The composition of the invention may also be used in a method ofproducing mechanical work or electricity, in particular, in accordancewith a Rankine cycle.

The invention also relates to a heat transfer system comprising a vapourcompression circuit containing the composition according to theinvention as a heat transfer composition, said circuit containing an oilseparator, and preferably a screw compressor.

According to one embodiment, this system is selected from mobile orstationary refrigeration, heating (heat pump), air conditioning andfreezing systems, and thermal engines.

This may concern in particular a heat pump system, in which case thefluid or body that is heated (usually air and possibly one or moreproducts, objects or organisms) is located in a room or a vehicleinterior (for a mobile system). According to a preferred embodiment, itis an air conditioning system, in which case the fluid or body that iscooled (generally air and possibly one or more products, objects ororganisms) is located in a room or vehicle interior (for a mobilesystem). It can be a refrigeration plant or a freezing facility (orcryogenic system), in which case the fluid or body that is cooledgenerally comprises air and one or more products, objects or organisms,located in a room or container.

In particular, the heat transfer system is a heat pump, or an airconditioning system, for example a chiller.

The invention also relates to a method for heating or cooling a fluid ora body by means of a vapour compression circuit containing a heattransfer composition, said method comprising successively theevaporation of the heat transfer composition, compression of the heattransfer composition, condensation of the heat transfer composition andexpansion of the heat transfer composition, wherein the heat transfercomposition is the composition according to invention described above,said compression circuit comprising an oil separator, and in particulara screw compressor.

The invention also relates to a method for producing electricity bymeans of a heat engine, said method comprising successively evaporationof the heat transfer composition, the expansion of the heat transfercomposition in a turbine allowing generating electricity, condensing theheat transfer composition and compressing the heat transfer composition,wherein the heat transfer composition is the composition describedabove, said method using an oil separator.

The vapour compression circuit containing a heat transfer compositioncomprises at least one evaporator, preferably a screw compressor, an oilseparator, a condenser and an expander, and heat transfer compositiontransport lines. between these elements. The evaporator and thecondenser comprise a heat exchanger for heat exchange between the heattransfer composition and another fluid or body.

The evaporator used in the context of the invention may be anoverheating evaporator or an embedded evaporator. In an overheatingevaporator, all of the heat transfer composition is evaporated at theevaporator outlet, and the vapour phase is superheated.

In a flooded evaporator, the heat transfer composition in liquid formdoes not evaporate completely. A flooded evaporator has a liquid phaseand vapour phase separator.

Regarding a compressor, a single or multi-stage centrifugal compressorin particular or a mini centrifugal compressor may be used. Rotary,piston or screw compressors may also be used.

According to one embodiment, the vapour compression circuit comprises acentrifugal compressor, and preferably a centrifugal compressor and aflooded evaporator.

According to another embodiment, the vapour compression circuitcomprises a screw compressor, preferably twin-screw or single-screw. Inparticular, the vapour compression circuit comprises a twin-screwcompressor, which can implement a substantial flow of oil, for exampleup to 6.3 L/s.

A centrifugal compressor is characterized in that it uses rotatingelements to accelerate radially the heat transfer composition; ittypically comprises at least one rotor and a diffuser housed in anenclosure. The heat transfer composition is introduced into the centreof the rotor and flows towards the periphery of the rotor whileundergoing acceleration. Thus, on the one hand, the static pressureincreases in the rotor, and especially on the other hand at the level ofthe diffuser, the speed is converted into an increase of the staticpressure. Each rotor/diffuser assembly constitutes a compressor stage.Centrifugal compressors may comprise from 1 to 12 stages, depending onthe desired final pressure and the volume of fluid to be treated.

The compression ratio is defined as the ratio of the absolute pressureof the output heat transfer composition to the absolute pressure of saidcomposition at the inlet.

The rotational speed for large centrifugal compressors ranges from 3000to 7000 revolutions per minute. Small centrifugal compressors (ormini-centrifugal compressors) generally operate at a rotation speedranging from 40000 to 70000 revolutions per minute and comprise a smallrotor (generally less than 0.15 m).

A multi-stage rotor can be used to improve the efficiency of thecompressor and to limit the energy cost (compared to a single-stagerotor). For a two-stage system, the output of the first stage of therotor feeds the input of the second rotor. Both rotors can be mounted ona single axis. Each stage can provide a fluid compression ratio of about4 to 1, i.e. the output absolute pressure can be about four times theabsolute suction pressure. Examples of two-stage centrifugalcompressors, particularly for automotive applications, are described inU.S. Pat. No. 5,363,674.

The centrifugal compressor can be driven by an electric motor or by agas turbine (for example powered by the exhaust gas of a vehicle, formobile applications) or by gearing.

The system may include coupling of the expander with a turbine togenerate electricity (Rankine cycle).

The system may also optionally comprise at least one heat transfer fluidcircuit used to transmit heat (with or without a change of state)between the circuit of the heat transfer composition and the fluid orbody to be heated or cooled.

The system may also optionally include two or more vapour compressioncircuits containing identical or different heat transfer compositions.For example, the vapour compression circuits may be coupled together.

The vapour compression circuit operates in a conventional vapourcompression cycle. The cycle comprises changing the state of the heattransfer composition from a liquid phase (or two-phase liquid/vapour) toa vapour phase at a relatively low pressure, and then compressing thevapour phase composition to a relatively high pressure, changing thestate (condensation) of the heat transfer composition from the vapourphase to the liquid phase at a relatively high pressure, and reducingthe pressure to restart the cycle.

In the case of a cooling process, heat from the fluid or the body thatis cooled (directly or indirectly, via a coolant) is absorbed by theheat transfer composition, during the evaporation of the latter, andthis at a relatively low temperature compared to the environment.Cooling processes include air conditioning processes (with mobilesystems, for example in vehicles, or stationary), refrigeration andfreezing or cryogenics. In the field of air conditioning, examplesinclude domestic, commercial or industrial air conditioning, where theequipment used is either chillers or direct expansion equipment. In thefield of refrigeration, examples include domestic and commercialrefrigeration, cold rooms, the food industry, refrigerated transport(trucks, boats).

In the case of a heating process, heat is transferred (directly orindirectly via a heat transfer fluid) from the heat transfercomposition, during the condensation thereof, to the fluid or to thebody that it heats at a relatively high temperature relative to theenvironment. The system for implementing the heat transfer is called inthis case “heat pump”. This can concern medium and high temperature heatpumps.

It is possible to use any type of heat exchanger for the implementationof the heat transfer compositions according to the invention, and inparticular co-current heat exchangers or, preferably, counter-currentheat exchangers.

However, according to a preferred embodiment, the invention anticipatesthat the cooling and heating processes, and the correspondingfacilities, comprise a counter current heat exchanger, either thecondenser or the evaporator. Indeed, the heat transfer compositionsaccording to the invention are particularly effective with countercurrent heat exchangers. Preferably, both the evaporator and thecondenser comprise a counter current heat exchanger.

According to the invention, the term “counter current heat exchanger” isunderstood to mean a heat exchanger wherein heat is exchanged between afirst fluid and a second fluid, the first fluid at the inlet of theexchanger exchanging heat with the second fluid at the outlet of theexchanger, and the first fluid at the outlet of the exchanger exchangingheat with the second fluid at the inlet of the exchanger.

For example, counter current heat exchangers include devices wherein theflow of the first fluid and the flow of the second fluid are in oppositeor almost opposite directions. The exchangers operating in cross currentmode with counter current tendency are also included among the countercurrent heat exchangers within the meaning of the present application.

Under different operating conditions (air conditioning, refrigeration,heat pump, etc.), the compositions according to the invention canadvantageously induce overheating at the outlet of the compressor(difference between temperature at the separator and temperature at thecondenser) greater than that of HFO-1234yf and/or HFO-1234ze.

In “low temperature refrigeration” processes, the inlet temperature ofthe heat transfer composition to the evaporator is preferably −45° C. to−15° C., especially −40° C. to −20° C., more preferably from −35° C. to−25° C. and for example about −30° C.; and the temperature of the onsetof condensation of the heat transfer composition at the condenser ispreferably 25° C. to 80° C., especially 30° C. to 60° C., morepreferably 35° C. to 55° C. and for example about 40° C.

In “moderate temperature cooling” processes, the inlet temperature ofthe heat transfer composition to the evaporator is preferably from −20°C. to 10° C., especially from −15° C. to 5° C. more preferably from −10°C. to 0° C. and for example about −5° C.; and the temperature of theonset of condensation of the heat transfer composition at the condenseris preferably 25° C. to 80° C., especially 30° C. to 60° C., morepreferably 35° C. to 55° C. and for example about 50° C. These processescan be refrigeration or air conditioning processes.

In “moderate temperature heating” processes, the inlet temperature ofthe heat transfer composition to the evaporator is preferably from −20°C. to 10° C., especially from −15° C. to 5° C. more preferably from −10°C. to 0° C. and for example about −5° C.; and the temperature of theonset of condensation of the heat transfer composition at the condenseris preferably from 25° C. to 80° C., especially from 30° C. to 60° C.,more preferably from 35° C. to 55° C. and for example about 50° C.

In “high temperature heating” processes, the inlet temperature of theheat transfer composition to the evaporator is preferably from −20° C.to 90° C., especially from 10° C. to 90° C., such as more preferablyfrom 50° C. to 90° C. and for example about 80° C.; and the temperatureof the onset of condensation of the heat transfer composition at thecondenser is preferably from 70° C. to 160° C., especially from 90° C.to 150° C., more preferably from 110° C. to 140° C. and for exampleabout 135° C.

The compositions according to the invention are particularly significantin refrigerated transport.

Refrigerated transport entails any movement of perishable products underrefrigerated space. Food or pharmaceutical products are an importantpart of perishable products.

Refrigerated transport can be carried out by lorry, rail or boat,possibly using multi-platform containers that also fit on lorries, railsor boats.

In refrigerated transport, the temperature of refrigerated spaces isbetween −30° C. and 16° C. The refrigerant charge in transport by lorry,rail or multi-platform containers varies between 4 kg and 8 kg ofrefrigerant. The systems in the boats can contain between 100 and 500kg.

The most used refrigerant to date is R404A.

The operating temperatures of the refrigerating plants depend on therefrigeration temperature requirements and the external climaticconditions. The same refrigeration system must be able to cover a widetemperature range of −30° C. to 16° C. and operate in both cold and hotclimates.

The most restrictive condition at evaporation temperature is −30° C.

Oil Separator

According to the invention, the vapour compression circuit comprises anoil separator.

According to one embodiment, the oil separator is located between thecompressor and the condenser.

According to the invention, the oil separator may be a tank or acylinder comprising at least one deflector or screen for collecting theoil.

According to one embodiment, the oil separator comprises afloat/valve/needle mechanism. In this particular case, the oil,recovered in the separator, is stored in the lower part containing thefloat/valve/pointer mechanism. When the oil level is high enough to liftthe float mechanism, the valve-needle system opens and allows the oil tore-enter the compressor housing(s). The oil return is carried out thanksto the pressure difference between that of the oil separator and that ofthe compressor crank house(s).

The oil separator advantageously makes it possible to separate thelubricating oil (lubricant) from the refrigerant in the gaseousrefrigerant mixture and the lubricating oil from the compressor. Inparticular, the oil separator allows the release of the refrigerant tothe condenser, and the return of the separated lubricating oil, to thecompressor.

The compression circuit according to the invention may comprise an oilreturn line between the oil separator and the inlet of the compressor.

In particular, the oil separator comprises an inlet valve (allowing inparticular the entry of the composition of the invention), an outletvalve in the upper part of the separator (in particular for recovering apart of the refrigerant which will go to the condenser), and an outletvalve in the lower part of the separator (allowing in particular theexit of the oil for its return to the compressor).

Typically, the oil separators can implement at least one of thefollowing techniques:

-   -   coalescence: a phenomenon by which two identical but dispersed        substances tend to reunite;    -   centrifugation: this technique uses centrifugal force to        separate fluids of different densities;    -   speed reduction: this technique allows the heavier molecules to        continue their trajectory, thanks to their inertia, while the        lighter molecules disperse in the internal volume of the oil        separator;    -   change of direction: this technique associated with the previous        one makes it possible to increase the separation efficiency of        the oil droplets (heavy molecules) present in the vapour (light        molecules). The oil droplets retain their initial trajectory, in        particular because of their weight and their initial velocity,        while the steam is directed towards the exit of the separator.

Coalescence can be performed using metal screens or coalescentcartridges.

Centrifugation can be performed using turbulators, helical systems orspecial arrangements of the separators (cyclone).

An oil separator can especially implement several of the aforementionedtechniques.

Examples of the oil separators that are useful according to theinvention are CarlyTURBOIL range, Danfoss OUB, Emerson OS, Castel 5520and 5540 series, Temprite separator and AC & R separators, Bitzer OASseparators for screw compressors.

The vapour compression circuit may further comprise an oil coolingsystem, and optionally an oil pump and/or an oil distribution system,located between the oil separator and the inlet of the compressor.

The oil pump can be used to remedy pressure losses and/or to allow theoil to reach a pressure higher than the discharge pressure of thecompressor.

The oil cooling system can be used to cool the oil from the compressorand oil separator.

Flammability

The preferred refrigerants F of the present invention furthermore havethe advantage of having a flame propagation velocity of less than 10cm/s, preferably less than 8 cm/s or even 7 cm/s or even 3 cm/sfollowing the measurement method developed by Jabbour T-2004. Somecompositions are even non-flammable.

The experimental setup uses the vertical glass tube method (number oftube 2, length 150 cm, diameter 40 cm). The use of two tubes facilitatestwo tests with the same concentration at the same time.

The tubes are equipped with tungsten electrodes, which are placed at thebottom of each tube, 6.35 mm (¼ inch) apart and connected to a 15 kV and30 mA generator.

The test method is developed in T. Jabbour's thesis, “Classification offlammability of refrigerants based on the fundamental flame velocity”under the direction of Denis Clodic. Thesis, Paris, 2004.

For example, the flame propagation speed for the compositionHFO-1234yf/R134a/R152a: 78.9/7.0/14.1% by weight is 4.75 cm/s and thatof the composition HFO-1234yf/R134a/R152a: 74.2/7.7/18.1% by weight is 6cm/s.

All the embodiments described above can be combined with each other.Thus, each preferred refrigerant of the composition can be combined witheach preferred polyol ester (esters A, B, C or D) in the variousproportions mentioned. The various preferred compositions can be used inthe various applications described above.

The following examples illustrate the invention but without limiting it.

FIG. 1: FIG. 1 is a diagram of the mixture R134a/Triton oil SE 55representing the temperature (in ° C.) on the abscissa and on theordinate the pressure (in bar), produced under the operating conditionsof the example below. At 0% oil, 100% R134a, while 70% oil has a mixturecomprising 30% R134a. This diagram shows that at constant pressure, therefrigerant concentration in the oil decreases as the temperature of themixture Ts increases.

EXAMPLES

Supplier of POE Triton SE 55 d Oil: FUCHS

In an oil separator integrated in a screw compressor, the oil isrecovered in the lower part of the separator. In this example, theamounts of refrigerant trapped by the oil in the separator are analysed.

The coolant/oil mixture in the separator is at a temperature Ts (whichis also the temperature of the refrigerant at the outlet of thecompressor) and the pressure in the separator is equal to therefrigerant vapour saturation pressure at the condenser inlet (Pcond).Therefore, this results in a system that works at a condensingtemperature (Tcond), which is the saturation temperature of therefrigerant alone at the corresponding Pcond pressure.

In general, the analysis of a typical refrigerant/oil diagram (as shownfor example in FIG. 1 for R134a) indicates that, at constant pressure(Pcond), the refrigerant concentration in the oil decreases when thetemperature of the mixture (oil/refrigerant, Ts) increases and movesaway from the saturation temperature of the refrigerant alone (Tcond),the difference between Ts and Tcond representing the overheating at theoutlet of the compressor.

Temperature Tcond, pressure Pcond and temperature Ts in the oilseparator are defined by the operating needs of the system. Thepercentage of oil in the refrigerant will therefore be deduced from thecorresponding refrigerant/oil diagram at the pressure Pcond and attemperature Ts. This method makes it possible to compare therefrigerants indirectly by watching overheating at the outlet of thecompressor.

Let us consider an air conditioning system that operates under thefollowing conditions in heating mode (heat pump):

-   -   Condensation temperature Tcond=70° C.;    -   Evaporation temperature: 0° C.;    -   Overheating on the evaporator: 0° C.;    -   Under cooling: 0° C.;    -   Compressor efficiency: 75%;    -   Reference case: R134a and POE Triton SE 55;

According to the diagram of FIG. 1, for a temperature (Ts) in theseparator of 87° C. and a pressure of 21 bar abs, the superheat at theoutlet of the compressor is 17° C. and the percentage of oil is 75%weight (25% weight of R134a in the oil).

For a HFO-1234yf/POE Triton SE 55 oil mixture, under the same operatingconditions as described above, the condenser pressure is about 20.5 barabs and the superheat at the compressor outlets about 4.8° C.

HFO-1234yf at saturation pressure very close to R134a but lowoverheating. As a result, the refrigerant concentration in the liquidphase of the oil separator will be greater than 30%, or even 35%, inweight.

Consequently, for the same oil/coolant liquid flow rate, increase of thepercentage of refrigerant in the oil of the separator resulted in adecrease in the amount of lubricating oil circulating in the compressorand also in a decrease of the viscosity of the oil/refrigerant mixture.Therefore, direct replacement of R134a with HFO-1234yf may damage thecompressor (lubrication problem, low viscosity) and decreaseperformance.

The table below provides the overheat value at the compressor outputcompared to the condensing temperature under the same operatingconditions, described above for R134a and HFO-1234yf, for differentmixtures:

The ratio A corresponds to the following relation:

$A = {\left\lbrack \frac{\begin{matrix}{{{overheating}\mspace{14mu} {of}\mspace{14mu} {compressor}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {mixture}} -} \\{{overheating}\mspace{14mu} {of}\mspace{14mu} {compressor}\mspace{14mu} {of}\mspace{14mu} 1234{yf}}\end{matrix}}{{overheating}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {compressor}\mspace{14mu} {of}\mspace{14mu} 1234{yf}} \right\rbrack \times 100}$

Temperature (° C.) condenser P (bar abs) evaporator compressor vapouroverheating condenser evaporator inlet output saturation compressor AHF0-1234y1 20.45 3.16 0.0 74.8 70.0 4.8 0 HF0-1234ze 16.11 2.17 0.0 77.270.0 7.2 50 R134a 21.17 2.93 0.0 87.6 70.0 17.6 266 R1234yf R134a 60.040.0 21.74 3.25 0.0 79.6 70.0 9.6 99 56.0 44.0 21.79 3.25 0.0 80.1 70.010.1 109 50.0 50.0 21.83 3.23 0.0 80.8 70.0 10.8 125 45.0 55.0 21.853.21 0.0 81.5 70.0 11.5 138 40.0 60.0 21.85 3.19 −0.1 82.1 70.0 12.1 152R134a R1234ze 42.0 58.0 18.77 2.53 −0.3 82.3 70.5 11.7 144 50.0 50.019.18 2.60 −0.3 83.0 70.5 12.6 161 55.0 45.0 19.42 2.64 −0.2 83.5 70.413.1 171 60.0 40.0 19.65 2.68 −0.2 84.0 70.4 13.6 182 R1234yf R152a 85.015.0 20.74 3.17 0.0 79.1 70.0 9.1 89 80.0 20.0 20.77 3.16 0.0 80.6 70.010.6 119 R152a R1234ze 5.0 95.0 16.61 2.23 −0.1 79.1 70.2 8.9 84 10.090.0 17.02 2.30 −0.2 80.7 70.3 10.4 116 15.0 85.0 17.36 2.36 −0.2 82.370.3 11.9 147 20.0 80.0 17.64 2.41 −0.2 83.7 70.3 13.4 177 25.0 75.017.88 2.45 −0.2 85.0 70.3 14.8 206

Temperature (° C.) P (bar abs) condenser con- evap- evaporatorcompressor vapour overheating denser orator inlet output saturationcompressor HF0-1234y1 20.45 3.16 0.0 74.8 70.0 4.8 0 HF0-1234ze 16.112.17 0.0 77.2 70.0 7.2 50 R134a 21.17 2.93 0.0 87.6 70.0 17.6 266R1234yf R134a R152a 81.5 8.5 10.0 20.95 3.19 0.0 78.7 70.0 8.7 81 77.58.5 14.0 20.95 3.18 0.0 79.9 70.0 9.9 105 76.5 8.5 15.0 20.95 3.17 0.080.2 70.0 10.2 111 71.5 8.5 20.0 20.92 3.15 0.0 81.7 70.0 11.6 142 66.58.5 25.0 20.88 3.12 −0.1 83.1 70.0 13.1 173 R134a R152a R1234ze 2.0 10.088.0 17.13 2.31 −0.2 81.0 70.3 10.6 121 5.0 10.0 85.0 17.30 2.34 −0.281.3 70.4 11.0 127 8.5 10.0 81.5 17.49 2.36 −0.2 81.7 70.4 11.3 135 2.015.0 83.0 17.46 2.37 −0.2 82.5 70.3 12.1 152 5.0 15.0 80.0 17.61 2.39−0.2 82.8 70.4 12.4 158 8.5 15.0 76.5 17.78 2.42 −0.2 83.1 70.4 12.8 1652.0 20.0 78.0 17.73 2.42 −0.2 83.9 70.3 13.6 181 5.0 20.0 75.0 17.862.44 −0.2 84.2 70.3 13.9 188 8.5 20.0 71.5 18.01 2.46 −0.2 84.5 70.314.2 195

The mixtures according to the invention advantageously have a compressoroverheating higher than the HFO-1234yf alone, and in particular acoefficient A, as defined above, greater than 50%, preferably greaterthan 80% in relation to HFO-1234yf.

Thus, the mixtures according to the invention advantageously can reduce(and/or avoid) the quantity of refrigerant trapped in the lubricatingoil in relation to HFO-1234yf alone, and therefore increase theefficiency of the system due to higher refrigerant circulation in thesystem. In addition, with the mixtures of the invention, the amount oflubricating oil recovered by the separator being higher than with theHFO-1234yf, a better lubrication of the compressor is obtained.

1. (canceled)
 2. The system according to claim 11, wherein the polyolesters have the following formula (I):R¹[OC(O)R²]_(n)   (I) wherein: R¹ is a linear or branched hydrocarbonradical, optionally substituted with at least one hydroxyl group and/orcomprising at least one heteroatom selected from the group consisting of—O—, —N—, and —S—; each R² is, independently of each other, selectedfrom the group consisting of: i) H; ii) an aliphatic hydrocarbonradical; iii) a branched hydrocarbon radical; iv) a mixture of a radicalii) and/or iii), with an aliphatic hydrocarbon radical comprising from 8to 14 carbon atoms; and n is an integer of at least
 2. 3. The systemaccording to claim 11, wherein the polyol esters are obtained from apolyol selected from the group consisting of neopentyl glycol, glycerol,trimethylolpropane, pentaerythritol, dipentaerythritol,tripentaerythritol, and mixtures thereof.
 4. The system according toclaim 11, wherein the polyol esters are obtained from at least onebranched carboxylic acid comprising from 5 to 8 carbon atoms.
 5. Thesystem according to claim 11, wherein the polyol esters are poly(neopentylpolyol) esters obtained by: i) reaction of a neopentylpolyolwith the following formula (V):

wherein: each R represents, independently of each other, CH₃, C₂H₅ orCH₂OH; p is an integer between 1 and 4; with at least one monocarboxylicacid containing 2 to 15 carbon atoms, in the presence of an acidcatalyst, the molar ratio between the carboxyl groups and the hydroxylgroups being less than 1:1, to form a composition of partiallyesterified poly (neopentyl) polyol; and ii) reacting the partiallyesterified poly (neopentyl) polyol composition obtained at the end ofstep i) with another carboxylic acid consisting from 2 to 15 carbonatoms, to form the poly (neopentyl polyol) ester composition.
 6. Thesystem according to claim 11, wherein the polyol esters have one of thefollowing formulas (VIII) or (IX):

in which: R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are, independently of each other,H or CH₃; a, b, c, y, x and z are, independently of each other, aninteger; a+x, b+y, and c+z are, independently of each other, integersranging from 1 to 20; R¹³, R¹⁴ and R¹⁵ are, independently of each other,selected from the group consisting of aliphatic or branched alkyls,alkenyls, cycloalkyls, aryls, alkylaryls, arylalkyls, alkylcycloalkyls,cycloalkylalkyls, arylcycloalkyls, cycloalkylaryls,alkylcycloalkylaryls, alkylarylcycloalkyls, arylcycloalkylalkyls,arylalkylcycloalkyls, cycloalkylalkylaryls and cycloalkylarylalkyls,R¹³, R¹⁴ and R¹⁵, consisting 1 to 17 carbon atoms, and may be optionallysubstituted. or

wherein: each of R¹⁷ and R¹⁸, is, independently of each other, H or CH₃;each of m and n is, independently of each other, an integer, with m+nbeing an integer from 1 to 10; R¹⁶ and R¹⁹ are, independently of eachother, selected from the group consisting of aliphatic or branchedaliphatic or branched alkyls, alkenyls, cycloalkyls, aryls, alkylaryls,arylalkyls, alkylcycloalkyls, cycloalkylalkyls, arylcycloalkyls,cycloalkylaryls, alkylcycloalkylaryls, alkylarylcycloalkyls,arylcycloalkylalkyls, arylalkylcycloalkyls, cycloalkylalkylaryls andcycloalkylarylalkyls, R¹⁶ and R¹⁹, consisting 1 to 17 carbon atoms, andmay be optionally substituted.
 7. The system according to claim 11,wherein the refrigerant F comprises at least one tetrafluoropropenechosen from HFO-1234yf and HFO-1234ze, and at least onehydrofluorocarbon selected from the group consisting of dichloromethane(HFC-32), pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane(HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane(HFC-152a), fluoroethane (HFC-161), 1,1,1,2,3,3,3-heptafluoropropane(HFC-227ea), 1,1,1-trifluoropropane (HFC-263fb), and mixtures thereof.8. The system according to claim 11, wherein refrigerant F comprises oneof the following mixtures: HFO-1234yf HFC-32 HFO-1234yf HFC-152aHFO-1234yf HFC-134a HFO-1234yf HFC-125 HFO-1234ze HFC-32 HFO-1234zeHFC-152a HFO-1234ze HFC-134a HFO-1234ze HFC-125 HFO-1234yf HFC-32HFC-125 HFO-1234yf HFC-152a HFC-125 HFO-1234yf HFC-152a HFC-32HFO-1234yf HFC-32 HFO-1234yf HFC-134a HFC-152a HFO-1234yf HFC-134aHFC-32 HFO-1234yf HFC-134a HFC-125 HFO-1234ze HFC-134a HFC-152aHFO-1234ze HFC-134a HFC-32 HFO-1234ze HFC-134a HFC-125 HFO-1234zeHFC-152a HFC-32 HFO-1234ze HFC-152a HFC-125 HFO-1234ze HFC-32 HFC-125HFO-1234yf HFO-1234ze HFC-134a HFO-1234yf HFO-1234ze HFC-152a HFO-1234yfHFO-1234ze HFC-134 HFO-1234yf HFO-1234ze HFC-32 HFO-1234yf HFO-1234zeHFC-125 HFO-1234yf HFC-134a HFC-152a HFC-32 HFO-1234yf HFC-134a HFC-152aHFC-125 HFO-1234yf HFO-1234ze HFC-134a HFC-32 HFO-1234yf HFO-1234zeHFC-134a HFC-152a HFO-1234yf HFO-1234ze HFC-134a HFC-125 HFO-1234yfHFC-32 HFO-1234ze HFC-134a HFC-152a HFC-32 HFO-1234ze HFC-134a HFC-152aHFC-125 HFO-1234yf HFC-134a HFC-152a HFC-125 HFC-32 HFO-1234ze HFC-134aHFC-152a HFC-125 HFC-32


9. The system according to claim 11, wherein refrigerant F comprisesfrom 75.5 to 79.5% weight of HFO-1234yf, from 12 to 16% weight ofHFC-152a, and from 6.5 to 10.5% weight of HFC-134a.
 10. The systemaccording to claim 11, wherein refrigerant F comprises 77.5% (±0.2%)weight of HFO-1234yf, 14% (±0.2%) weight of HFC-152a and 8.5% (±0.2%)weight of HFC-134a, said composition being azeotropic at a boiling pointof between −40.00° C. and 70.00° C., at a pressure between 0.5 and 21.0bar abs (±0.5%).
 11. A heat transfer system comprising a vapourcompression circuit containing a composition comprising a polyol esterlubricant, and a refrigerant F comprising at least onetetrafluoropropene and at least one hydrofluorocarbon, as a heattransfer composition, said vapour compression circuit comprising an oilseparator.
 12. The system according to claim 11, selected from mobile orstationary heat pump heating, air conditioning, refrigeration, andfreezing systems, and thermal engines.
 13. A method of producingelectricity by means of a heat engine, said method comprisingsuccessively evaporation of the heat transfer composition, expansion ofthe heat transfer composition in a turbine for generating electricity,condensation of the heat transfer composition, and compression of theheat transfer composition, wherein the process comprising using an oilseparator, and said heat transfer composition being a compositioncomprising a lubricant based on polyol esters, and a refrigerant fluid Fcomprising at least one tetrafluoropropene and at least onehydrofluorocarbon.
 14. A method of heating or cooling a fluid or a bodyby means of a vapour compression circuit containing a heat transfercomposition, said method comprising successively evaporation of the heattransfer composition, compression of the heat transfer composition, thecondensation of the heat transfer composition and the expansion of theheat transfer composition, said compression circuit comprising an oilseparator, and said heat transfer composition being a compositioncomprising a lubricant based on polyol esters, and a refrigerant fluid Fcomprising at least one tetrafluoropropene and at least onehydrofluorocarbon.